The word's origin and meaning are uncertain. While the sense of 'religious hypocrite or fanatic' appeared in Middle French in the late 15th century and subsequently entered English in the early 16th, the OED highlights the lack of connection between these later uses and earlier 12th-century examples. The FEW suggests an etymology linking the word to the English oath 'by God', supposedly sworn by Rollo, the Viking founder of Normandy, in the early 10th century. However, this theory, based on a 13th-century chronicle by Matthew Paris, is considered historically and linguistically unfounded (see Family Names Bygott for a discussion).